ADX is used to quantify trend strength. ADX calculations are based on a moving average of price range expansion over a given period of time. The default setting is 14 bars, although other time periods can be used.1 ADX can be used on any trading vehicle such as stocks, mutual funds, exchange-traded funds and futures.
ADX is plotted as a single line with values ranging from a low of zero to a high of 100. ADX is non-directional; it registers trend strength whether price is trending up or down.2 The indicator is usually plotted in the same window as the two directional movement indicator (DMI) lines, from which ADX is derived (shown below).
For the remainder of this article, ADX will be shown separately on the charts for educational purposes.
When the +DMI is above the -DMI, prices are moving up, and ADX measures the strength of the uptrend. When the -DMI is above the +DMI, prices are moving down, and ADX measures the strength of the downtrend. The chart above is an example of an uptrend reversing to a downtrend. Notice how ADX rose during the uptrend, when +DMI was above -DMI. When price reversed, the -DMI crossed above the +DMI, and ADX rose again to measure the strength of the downtrend.